There are numerous different wireless communication networks with which user devices such as electronic book readers, cellular telephones, personal digital assistants (PDAs), portable media players, tablet computers and netbooks may connect. Each of these wireless communication devices may use different wireless communication technologies. Wireless communication technologies are roughly categorized into first generation (1G), second generation (2G), third generation (3G) and fourth generation (4G) wireless communication technologies. One emerging 4G wireless communication technology is 3rd Generation Partnership Project (3GPP) long term evolution (LTE), commonly referred to simply as LTE.
LTE is a packet switched network technology that supports only packet services, and does not support circuit switched services. Traditional voice calls are circuit switched services. Voice over internet protocol (VOIP) is a packed switched service for enabling voice communication in a packet switched network. Accordingly, when a device that is connected to an LTE network is to make a voice call, it can either user VOIP over LTE (VOLTE) or perform a circuit switched fallback. Most LTE networks currently do not support VOLTE. Therefore, a majority of LTE networks rely on circuit switched fallback to enable voice communications.
Circuit switched fallback is a procedure to transfer a device from an LTE network to a legacy network such as a 3G network or a 2G network. As circuit switched fallback is currently implemented, to perform circuit switched fallback, a user device must have an active radio connection to the LTE network. This means that a user device that is in an idle state must first establish a connection to the LTE network and then wait for the LTE network to transfer the connection to a legacy network before a voice call can be initiated. This can delay the initiation of a voice call by a second or more.